Catheters for electromagnetic ablation are known and are commonly used to treat various diseases and medical disorders. Typically, the catheter includes an energy-delivering electrode that is coupled to a source of electromagnetic energy, e.g., an electrosurgical generator. Other electrodes can be proximally positioned on the catheter and can be used for sensing and other related electrical purposes.
In prior procedures, an ablation catheter is employed to alter tissue. In order to ablate the tissue, electromagnetic energy is applied to create a lesion via the energy-delivering electrode without regard to the specific level of electromagnetic energy supplied by the generator. In situations where too much electromagnetic energy is delivered to the tissue during the electrosurgical procedure, the tissue “pops”, thus indicating the application of an excessive amount of energy.
Several clinical conditions comprise transitory or permanent autonomic dysfunction by increasing the vagal action and sympathetic driving reduction. As a consequence, transitory or permanent, symptomatic or asymptomatic sinus bradycardias or pauses or transitory AV block may occur. The most typical examples are the cardio inhibitory or mixed neurocardiogenic syncope, carotid sinus syndrome and the functional transitory AV block.
Despite having apparently normal hearts, these patients may be very symptomatic and refractory to conventional medication. Consequently they represent a difficult problem for the cardiologist as far as many of them are referred to the permanent pacemaker implantation. Furthermore we have to add to this group a considerable number of patients presenting a significant sinus and AV node dysfunction with good atropine response suggesting that an important portion of the vagal innervations is still preserved.
A pacemaker has been used, as the last option, to treat the malignant neurocardiogenic syncope (Sutton R. How and when to pace in vasovagal syncope. J Cardiovasc Electrophysiol. 2002 January; 13(1 Suppl):S14-6; Sutton R. Has cardiac pacing a role in vasovagal syncope? J Interv Card Electrophysiol. 2003 October; 9(2):145-9; Benditt D G, Sutton R, Gammage M D, et al.: Clinical experience with Thera DR rate-drop response pacing algorithm in carotid sinus syndrome and vasovagal syncope. The International Rate-Drop Investigators Group. Pacing Clin Electrophysiol 1997, 20:832-839; Kurbaan A S, Franzen A C, Heaven D, Mathur G, Bowker T J, Petersen M, Sutton R. Cardioinhibition during tilt testing identifies patients who may benefit from pacing. Pacing Clin Electrophysiol. 2000 November; 23(11 Pt 2):1792-4.) Its indication is uncomfortable in a young and apparently normal heart patient. Furthermore, recent studies have shown the cardiac stimulation has not been a good solution for all the cases of neurocardiogenic syncope. Several studies have shown that a great number of parasympathetic efferent fibers and autonomic ganglia surround the sinus and AV nodes regions (Connolly S J, Sheldon R, Thorpe K E, Roberts R S, Ellenbogen K A, Wilkoff B L, Morillo C, Gent M; VPS II Investigators.—Pacemaker therapy for prevention of syncope in patients with recurrent severe vasovagal syncope: Second Vasovagal Pacemaker Study (VPS II): a randomized trial. JAMA. 2003 May 7; 289(17):2224-9; Geis W P, Kaye M P, Randall W C. Major autonomic pathways to the atria and S-A and A-V nodes of the canine heart. Am J Physiol. 1973; 224:202-208. [Medline]; Lazzara R, Scherlag B J, Robison M J, Samet P. Selective in situ parasympathetic control of the canine sinoatrial and atrioventricular nodes. Circ Res. 1973; 32:393-401. [Medline]; Billman G E, Hoskins R S, Randall D C, Randall W C, Hamlin R L, Lin Y C. Selective vagal postganglionic innervation of the sinoatrial and atrioventricular nodes in the non-human primate. J Auton Nerv Syst. 1989; 26:27-36. [Medline].